APPLICATION OF COMPLEMENT FIXATION 187 



clinical value of the reaction. The widespread use of the reaction has 

 led to marked advances in the understanding of this disease, its sequelae 

 and its treatment. This application of the Bordet-Gengou phenomenon 

 has enabled science to progress far toward the elimination of one of 

 the greatest plagues of mankind. Wassermann and his collaborators 

 had first shown that the Bordet-Gengou phenomenon was applicable 

 not only to bacterial suspensions but also to bacterial extracts and from 

 this developed the proposition that the causative agent of syphilis 

 might act as an antigen in extracts from syphilitic organs. The test 

 was originally performed with a salt solution extract of the liver or 

 spleen of a syphilitic fetus (rich in treponema pallidum), inactivated 

 human serum, guinea-pig complement, an inactivated hemolytic im- 

 mune serum and sheep erythrocytes. All the reagents were tested and 

 titrated to avoid factors of error and proper controls were instituted in 

 each experiment. Much has been accomplished by further study in the 

 hands of numberless investigators, but we shall limit our discussion 

 to those features which are of fundamental importance in the under- 

 standing and application of the test. 



The Antigen. The preparation of the antigen is one of the most 

 important features of this test. It would be supposed that an extract 

 of a pure culture of the treponema pallidum should give the most 

 specific results. This, however, has not proved to be the case. It is 

 difficult to grow the organism in pure culture and the method of culti- 

 vation interposes difficulties in the way of obtaining pure extracts. 

 Results are variable and therefore not so specific as with the use of 

 other antigens. Until recently the organism had not been cultured in 

 vitro and Wassermann and many of his successors were unable to 

 utilize the method. Wassermann selected the organs of syphilitic 

 fetuses, because they were known to contain large numbers of tre- 

 ponemata, and from these made extracts in physiologic salt solution. 

 He cut syphilitic fetal liver in fine pieces and mixed 100 grams liver 

 with 360 c.c. physiologic salt solution and 40 c.c. 5 per cent, phenol 

 solution. This was shaken for twenty-four hours, centrifuged and the 

 supernatant fluid employed as antigen. Practical experience shows that 

 these antigens vary considerably in strength and rapidly lose fixing 

 power. Deterioration may result from light, air, warmth and freezing, 

 so that the extract must be kept tightly stoppered in the dark at low 

 but not freezing temperature. Marie and Levaditi dried and pulverized 

 the liver in order to preserve it and made up salt solution extracts when 

 needed. Morgenroth and Stertz preserved the organ in the frozen 

 state. The subsequent work of Weil and of Lansteiner and their col- 

 leagues indicated that tumor extracts, extracts of animal tissues and 

 of normal human tissues would operate as antigens. More recently 

 Varney and Baeslack have employed extracts of experimentally inocu- 

 lated testes of the rabbit in that stage of infection when the organs are 

 richly infiltrated with the treponema. 



Landsteiner, Muller and Potzl found that alcoholic extracts of 

 guinea-pig heart serve admirably as antigen. Independently Porges 



